Oligomeric compounds with acid-labile protective groups useful in positive-working radiation-sensitive mixture

ABSTRACT

Disclosed are compounds of the formula I ##STR1## in which X is a phenyl, [1]naphthyl or [2]naphthyl radical each substituted by at least one tert.-butoxycarbonyloxy group and, if appropriate, having one or more than one additional substituent, 
     R 1  is a hydrogen atom, a (C 1  -C 6 )-alkyl radical, a (C 6  -C 10 )-aryl radical or one of the radicals X and 
     R 2  is a (C 4  -C 12 )-alkylene, (C 4  -C 12 )-alkenylene or (C 4  -C 12 )-alkynylene group in which, if appropriate, up to three methylene groups are replaced by bridge members having at least one hetero atom, such as --O--, --S--, --NR 3  --, --CO--, --CO--O--, --CO--NH--, --O--CO--NH--, --NH--CO--NH--, --CO--NH--CO--, --SO 2  --, --SO 2  --O-- or --SO 2  --NH--, a (C 4  -C 12 )-cycloalkylene, (C 4  -C 12 )-cycloalkenylene or (C 8  -C 16 )-arylenebisalkyl radical in which, if appropriate, up to three methylene groups of the aliphatic moiety are replaced by bridge members of the above-mentioned type and which can be substituted in the aromatic moiety by fluorine, chlorine or bromine atoms or by (C 1  -C 4 )-alkyl, (C 1  -C 4 )-alkoxy, nitro, cyano or tert.-butoxycarbonyloxy groups, 
     R 3  being an acyl radical, especially a (C 1  -C 6 )-alkanoyl radical, and 
     n being an integer from 2 to 50, preferably from 5 to 20.

BACKGROUND OF THE INVENTION

The present invention relates to oligomeric compounds with acid-labileprotective groups, to processes for the preparation of these compoundsand to positive-working radiation-sensitive mixtures containing thesecompounds as solubility inhibitors. It also relates to a recordingmaterial prepared with these compounds, which is suitable forphotoresists, electrical components and printing plates and also forchemical milling.

In the industrial manufacture of microelectronic components, a number oflithographic techniques are currently used, different demands being madein each case on the photoresist mixtures used therein. Thus, in g-linelithography, where radiation of a wavelength of 436 nm is employed,conventional diazonaphthoquinone/novolak photoresists are generallyused. A more recent development is i-line lithography, in whichradiation of a wavelength of 365 nm is used. Images with details of amask original in improved resolution down to 0.5 μm can be obtained withthis technique. More recent modifications, such as phase-shifting masktechnology, permit a further reduction in image size down to about 0.35μm and even finer. Even better resolution will become possible in thefuture by means of the "UV-2" photoresists. A distinction is here madebetween two variants: UV-2 wide-band irradiation (240 to 260 nm) andirradiation with KrF-excimer lasers (248 nm).

As can already be seen from the above, the limit of resolution is givenby the wavelength of the radiation used. The continuing reduction insize of the structural dimensions, far down into the submicron region,especially for microchips, requires modified lithographic techniques.Because of their short wavelength, high-energy UV radiation, electronbeams or X-rays are here particularly suitable. A review of the demandsthat are made on the radiation-sensitive mixtures used in a particularcase, will be found in the article by C. G. Willson, "Organic ResistMaterials--Theory and Chemistry" (Introduction to Microlithography,Theory, Materials and Processing; Editors: L. F. Thompson, C. G.Willson, M. J. Bowden; ACS Symp. Ser., 219: 87 (1983), American ChemicalSociety, Washington). There is therefore an increased demand forradiation-sensitive mixtures that can be used in the advancedtechnologies, especially in mid-UV lithography, deep-UV lithography,electron lithography and X-ray lithography. In addition, they arepreferably sensitive within a wide spectral range and can thus also beused in conventional UV lithography.

A frequently used positive-working radiation-sensitive mixture forproducing radiation-sensitive recording materials contains ano-quinonediazide derivative and a binder that is soluble inaqueous-alkaline solutions, for example, a novolak or apolyhydroxystyrene. However, the sensitivity of the recording materialsto UV radiation, in particular high-energy short-wave radiation, forexample, to the light of a KrF-excimer laser having a wavelength of 248nm, or to electron beams is generally insufficient.

Positive-working radiation-sensitive mixtures in which a photo initiatorgenerates an acid as a result of the action of actinic radiation show animproved sensitivity. In a subsequent reaction, this acid cleaves anacid-cleavable material and thereby renders it soluble inaqueous-alkaline developers.

It is also known that compounds having phenolic OH groups can be"masked" by tert.-butoxycarbonyl groups. Acids cleave this derivativeinto the phenolic starting compound, carbon dioxide and isobutene. Suchcompounds can also be utilized as light-sensitive solubility inhibitors.

Radiation-sensitive mixtures with acid-cleavable solubility inhibitorsalways require a small quantity of a compound that, on irradiation,generates an acid that in turn effects the cleavage of theabove-mentioned materials. As photolytic acid generators, onium salts,such as diazonium, phosphonium, sulfonium and iodonium salts ofnon-nucleophilic acids, such as HSbF₆, HAsF₆ or HPF₆, have especiallybeen used. In addition, halogen compounds, especiallytrichloromethyltriazine derivatives or trichloromethyloxadiazolederivatives, o-quinonediazidesulfochlorides, o-quinonediazide-4-sulfonicacid esters, organometal/organohalogen combinations,bis(sulfonyl)diazomethanes, sulfonylcarbonyl-diazomethanes ornitrobenzyl tosylates have been recommended.

Such mixtures, some of which have high sensitivities to actinicradiation, are called photocatalytic 3-component systems, since theycontain, as essential constituents, a polymeric binder soluble inaqueous-alkaline solutions (in most cases a phenolic resin), aphotoactive compound and an acid-cleavable solubility inhibitor. Amongthese mixtures, those have gained particular acceptance in practicewhich contain compounds with acetal groups as the acid-labile component,since these combine adequate cleavability on the one hand with adequatestorage stability on the other hand, especially in the dissolved form.The acetal must here have, inter alia, a largely hydrophobic molecularbackbone, in order to be able to function as a solubility inhibitor.Acetals having free phenolic hydroxyl groups are completely unsuitableas solubility inhibitors, since they enhance the solubility inaqueous-alkaline solutions.

Furthermore, it can be observed generally that the process window, i.e.,the spectral range of transmission for the exposure of these mixtures,is very narrow and frequently not unambiguously reproducible, causinginaccurate reproductions of the original. The inadequately narrowprocess window manifests itself especially in a steep dependency of thequality of image reproduction on the time difference between exposureand development, the so-called delay time. The causes of thisdeterioration in the image reproduction are not known in detail or havenot been adequately investigated. In principle, it must be assumed thatdiffusion processes, which cause this behavior, cannot readily becontrolled. However, it may be supposed that, during the drying of themixture on a substrate material, a partial vaporization of thephotoinitiator or of the acid-labile compound or a segregation of theindividual mixture constituents takes place. This is particularlyfrequently observed in the case of acid-labile compounds having a lowsolubility in the usual coating solvents.

The decisive disadvantage of the known compounds containing acetalgroups is the fact that the solubility differentiation between exposedand unexposed image areas, resulting from the cleavage of thesecompounds, is generally insufficient. It appears that either the acetalderivative used as the solubility inhibitor has an inadequate inhibitingproperty and, in addition to the exposed image areas, those which havenot been exposed are also severely attacked and worn off duringimagewise differentiation, or that the exposed areas do not have anadequate solubility to allow imagewise differentiation duringdevelopment. The problem is that the known compounds are unable toprovide a material that causes a sufficiently large solubilitydifference between exposed and unexposed areas. Whereas this effect isstill generally acceptable in the case of the novolak resins usedaccording to the state of the art, it is observed, when other polymersare used, that the known acetal derivatives virtually cease to show anyinhibiting action and therefore no longer allow an image differentiationas required in practice.

In the acid-catalyzed cleavage of 1 mol of the acetal, 1 mol of thecorresponding aldehyde and 2 mol of alcohol are formed. In general, thealcohol contributes to the improved solubility in alkaline developers.By contrast, the aldehyde reduces the solubility, so that it isfrequently evaporated out of the mixture by means of an additionalbaking step. It is more advantageous, however, to leave the aldehyde inthe layer composed of the mixture, since it can be evaporated only in anuncontrollable manner, especially in the case of different layerthicknesses. This leads to non-reproducible results with respect tosensitivity and development behavior.

In both cases, best results are therefore not obtained. If thesolubility-inhibiting aldehyde generated by cleavage has to beevaporated out of the mixture, an additional processing step isnecessary in order to obtain the best possible solubility of the exposedareas. If the aldehyde having an inhibiting action remains in themixture, a differentiation of the solubility between exposed andunexposed layer areas, as required in practice, is not achieved. Thishas in turn particularly disadvantageous consequences if the mixture isused in a recording material. In this case, longer exposure anddevelopment times must be accepted, and the resulting relief image has,due to the inadequate solubility differentiation between exposed andunexposed areas, weaknesses in contrast, in the structural profile andin the wearing-off in the dark.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide compoundsthat effectively reduce the solubility in water, that have cleavageproducts that are very readily soluble in aqueous-alkaline developers,assisting the developing process in the exposed areas, and that have alow volatility, so that they do not evaporate out of the mixture evenduring a thermal aftertreatment, so that the properties of theradiation-sensitive mixture remain controllable.

These and other objects according to the invention are achieved by acompound of the formula I ##STR2## in which X is a phenyl, [1]naphthylor [2]naphthyl radical that is substituted by at least onetert.-butoxycarbonyloxy group and optionally by further substituents,

R¹ is a hydrogen atom, a (C₁ -C₆)-alkyl radical, a (C₆ -C₁₀)-arylradical or one of the radicals X and

R² is a (C₄ -C₁₂)-alkylene, (C₄ -C₁₂)-alkenylene or (C₄ -C₁₂)-alkynylenegroup in which up to three methylene groups are optionally replaced bybridge members having at least one hetero atom, said bridge membersbeing selected from the group consisting of --O--, --S--, --NR³ --,--CO--, --CO--O--, --CO--NH--, --O--CO--NH--, --NH--CO--NH--,--CO--NH--CO--, --SO₂ --, --SO₂ --O-- and --SO₂ --NH--, a (C₄-C₁₂)-cycloalkylene radical, a (C₄ -C₁₂)-cycloalkenylene radical, or a(C₈ -C₁₆)-arylenebisalkyl radical, up to three methylene groups of thealiphatic moiety of the (C₈ -C₁₆)-arylenebisalkyl radical beingoptionally replaced by bridge members of the above-mentioned type andthe aromatic moiety of the (C₈ -C₁₆)-arylenebisalkyl radical beingoptionally substituted by fluorine, chlorine or bromine atoms or by (C₁-C₄)-alkyl, (C₁ -C₄)-alkoxy, nitro, cyano or tert.-butoxycarbonyloxygroups,

R³ being an acyl radical, and

n being an integer from 2 to 50.

A process for preparing a compound according to formula I is alsoprovided, which comprises the steps of converting, in a first stage, analdehyde or ketone of the formula II

    X--CO--R.sup.1

by means of a low-boiling alcohol in the presence of a catalyst and of adehydrating agent into an acetal or ketal of the formula III ##STR3##and then converting the acetal or ketal of formula III, in a secondstage, by reaction with a bifunctional alcohol HO--R² --OH in thepresence of a catalyst into the compound of the formula I.

A positive-working radiation-sensitive mixture according to theinvention comprises (a) a compound that generates a strong acid underthe action of actinic radiation, (b) a compound as claimed in claim 1having at least one C--O--C bond that can be cleaved by the acidgenerated by the compound (a), and (c) a binder that is insoluble inwater but soluble or at least swellable in aqueous-alkaline solution. Aradiation-sensitive recording material comprises a layer of this mixturecoated on a substrate.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Novel oligomeric substituted acetals and ketals are provided accordingto the invention that are cleaved under the action of a sufficientlystrong acid and thereby release a hydroxy-substituted aromatic aldehydeor a hydroxy-substituted aromatic ketone.

The novel compounds are represented by the formula ##STR4## in which Xis a phenyl, [1]naphthyl or [2]naphthyl radical each substituted by atleast one tert.-butoxycarbonyloxy group and, if appropriate, having oneor more than one additional substituent,

R¹ is a hydrogen atom, a (C₁ -C₆)-alkyl radical, a (C₆ -C₁₀)-arylradical or one of the radicals X and

R² is a (C₄ -C₁₂)-alkylene, (C₄ -C₁₂)-alkenylene or (C₄ -C₁₂)-alkynylenegroup in which, if appropriate, up to three methylene groups arereplaced by bridge members having at least one hetero atom, such as--O--, --S--, --NR³ --, --CO--, --CO--O--, --CO--NH--, --O--CO--NH--,--NH--CO--NH--, --CO--NH--CO--, --SO₂ --, --SO₂ --O-- or --SO₂ --NH--, a(C₄ -C₁₂)-cycloalkylene, (C₄ -C₁₂)-cycloalkenylene or (C₈-C₁₆)-arylenebisalkyl radical in which, if appropriate, up to threemethylene groups of the aliphatic moiety are replaced by bridge membersof the above-mentioned type and which can be substituted in the aromaticmoiety by fluorine, chlorine or bromine atoms or by (C_(1-C) ₄)-alkyl,(C₁ -C₄)-alkoxy, nitro, cyano or tert.-butoxycarbonyloxy groups,

R³ being an acyl radical, especially a (C₁ -C₆)-alkanoyl radical, and

n being an integer from 2 to 50, preferably from 5 to 20.

The substituents that may additionally be present in the radicals X arepreferably fluorine, chlorine, bromine or iodine atoms, nitro, cyano orcarboxyl groups, (C₁ -C₉)- and particularly preferably (C₁ -C₆)-alkylradicals in which, if appropriate, up to three and particularlypreferably up to two methylene groups are replaced by bridge members ofthe above-mentioned type, phenyl radicals that may in turn besubstituted, especially by tert.-butoxycarbonyl groups, (C₁ -C₄)-alkylradicals, (C₁ -C₄)-alkoxy radicals and/or halogen atoms, and also (C₈-C₁₂)- and particularly preferably (C₈ -C₁₀)-aralkyl radicals in which,if appropriate, up to two methylene groups are replaced by bridgemembers of the above-mentioned type, (C₆ -C₁₀)-aryloxy radicals or (C₇-C₁₀)-aralkoxy radicals.

The bridge members containing hetero atoms in the alkyl and aralkylradicals can be present within the alkyl chain or represent the memberlinked to the radical X.

Compounds of the formula I in which X is a substituted phenyl radicalare generally preferred. Compounds of the formula I in which R¹,furthermore, is a hydrogen atom are particularly preferred.

The compounds according to the invention represent acetals or ketalsthat have a pronounced hydrophobic character and are therefore suitableas solubility inhibitors, whereas the products resulting from theacid-catalyzed cleavage of these compounds are extraordinarilyhydrophilic and therefore act as solubility enhancers.

The invention further relates to a process for preparing the compoundsof the formula I, wherein a carbonyl compound of the formula II

    X--CO--R.sup.1

in which X and R¹ have the definitions given above, are reacted with alow-boiling alcohol in the presence of a catalyst to give thecorresponding acetals or ketals of the formula III ##STR5##

The low-boiling alcohol is preferably methanol or ethanol, i.e., m ispreferably 1 or 2.

In order irreversibly to remove the water of reaction that is formedduring the reaction, the mixture advantageously contains a suitabledehydrating agent, for example, a drying agent.

The compounds according to the invention of the formula I are thenobtained by reaction with bifunctional alcohols HO--R² --OH in thepresence of a catalyst. If appropriate, it is also possible to add smallamounts of a polyfunctional alcohol, as a result of which an incipientoligomer is obtained.

The compounds of the formula II can be prepared from the correspondingaromatic aldehydes or ketones substituted by hydroxy groups in a mannerknown per se (F. Houlihan et al., Can. J. Chem., 63: 153 (1985)) byreaction with tert.-butoxycarbonyl chloride or di-tert.-butylpyrocarbonate.

Particularly preferred starting materials are hydroxy-substitutedaromatic aldehydes such as 2-, 3- and 4-hydroxybenzaldehyde, 2,3-, 2,4-,2,5- and 3,4-dihydroxybenzaldehyde, 2,3,4-trihydroxybenzaldehyde,4-hydroxy-3-methylbenzaldehyde, 2-hydroxy-4- and -5-methoxybenzaldehyde,3-hydroxy-4-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde,3,5-dimethyl-4-hydroxybenzaldehyde, 3,4-dimethoxy-5-hydroxybenzaldehyde,3-ethoxy-4-hydroxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde,3-hydroxy-4-nitrobenzaldehyde, 4-hydroxy-3-nitrobenzaldehyde,5-hydroxy-2-nitrobenzaldehyde or 2-hydroxy-1-naphthaldehyde.

These aldehydes are commercially available, whereas other aromatichydroxy-aldehydes or -ketones likewise suitable as precursors can ingeneral be prepared in a simple manner by the most diverse methods (seeHouben Weyl, METHODEN DER ORGANISCHEN CHEMIE [METHODS OF ORGANICCHEMISTRY], volume 7/1).

To avoid cleavage of the tert.-butoxycarbonyloxy group, theacetalization or ketalization of the compounds of the formula II iscarried out with the low-boiling alcohols in the presence of a specialcatalyst. Catalysts of the type of the rhodium phosphine complexes haveproven suitable. Catalysts of the RhCl₃ (triphos) type are preferred.Particularly preferred is the catalyst RhCl₃ [CH₃ C(CH₂ PPh₂)₃ ].

The required quantity of the catalyst is generally between about 0.1 mgand 10 mg per 1 mmol of aldehyde, and preferably between about 0.5 and 1mg of catalyst per 1 mmol of aldehyde. These catalysts have beendescribed by J. Ott et al. in J. Organomet. Chem., 291: 89 (1985) andTetrahedr. Lett., 30:6151 (1989).

The acetalization or ketalization is advantageously carried out attemperatures between about 0° C. and 100° C. Temperatures between about10° C. and 50° C., especially room temperature, are preferred. Thereaction time is between 20 minutes and 48 hours, especially betweenabout 4 and 16 hours.

The reaction can be carried out in the presence of a solvent that isinert under the reaction conditions. Aromatic hydrocarbons such astoluene and xylene are particularly suitable. The solvent is added in a0.5 to 50-fold excess.

For irreversible removal of the water of reaction formed, the trialkylorthoformate corresponding to the alcohol, preferably trimethyl ortriethyl orthoformate, is added to the reaction mixture.

The mixture is worked up by known methods. Yields of more than 90% areobtained.

The acetalization or ketalization of the compounds of the formula II canalso be carried out in the presence of other neutral or very weaklyacidic catalysts, such as acidic exchanger resins or organic acids.However, these catalysts lead to an incomplete conversion or totransesterification and hence to difficulties in working-up and to areduction in the product yield and purity.

With the above-mentioned rhodium catalysts, the aldehydes or ketones ofthe formula II can also be reacted directly with the bifunctionalalcohols HO--R² --OH. However, this raises problems in working-up, whichdo not arise in the two-stage process described above.

The compounds according to the invention of the formula I are thenobtained from the compounds of the formula III in a second stage byreaction with a higher-boiling dihydric alcohol R² (OH)₂ in an inertsolvent, such as toluene or xylene, in the presence of an acidiccatalyst. Here again, in order to avoid decomposition of thetert.-butoxycarbonyloxy group, only weakly acidic catalysts insoluble inthe reaction mixture are used. Potassium hydrogen sulfate or an acidicion exchanger resin are preferably used as catalyst.

For each mmol of acetal or ketal employed, 1 to 100 mg of catalyst areused. The preferred quantity ratio is 5 to 10 mg of catalyst/mmol ofcarbonyl derivative. To increase the reaction rate, the reaction iscarried out at temperatures of more than about 75° C., and temperaturesbetween about 100° and 150° C. are preferred.

The compounds of the formula I are in general obtained from thecompounds of the formula III in a yield of about 50 to 85% of thattheoretically possible.

The compounds according to the invention of the formula I areoutstandingly suitable for the preparation of positive-workingradiation-sensitive mixtures which can be used in radiation-sensitivelayers for photo-resists or printing plates.

The present invention further relates to a positive-workingradiation-sensitive mixture with

(a) a compound that generates a strong acid under the action of actinicradiation,

(b) a compound having at least one C--O--C bond that can be cleaved bythe acid generated by the compound (a), and

(c) a binder that is insoluble in water but soluble or at leastswellable in aqueous-alkaline solution,

wherein the compound (b) is a compound of the formula I.

The radiation-sensitive mixture according to the invention isdistinguished by high sensitivity and a wide spectral range. It showshigh thermal stability and allows even superfine structures of anoriginal to be reproduced in true detail.

The content of acid-cleavable material (b) in the radiation-sensitivemixture according to the invention should be about 1 to 60% by weightand preferably about 5 to 50% by weight, each relative to the totalweight of the solid constituents of the mixture.

If desired, the mixtures according to the invention can also containother acid-cleavable compounds. Above all the following classes ofcompounds have proven suitable for this purpose:

1. those having at least one orthocarboxylate and/ororthocarboxamide-acetal grouping, it also being possible for thecompounds to have a polymeric character and for the said groupings toappear as linking elements in the main chain or as side-chainsubstituents (DE 2,610,842 and 2,928,636),

2. oligomeric or polymeric compounds having recurring acetal and/orketal groupings in the main chain (DE 2,306,248 and 2,718,254),

3. compounds having at least one enol ether or N-acyliminocarbonategrouping (EP 0,006,626 and 0,006,627),

4. cyclic acetals or ketals of β-keto-esters or -amides (EP 0,202,196),

5. compounds having silyl ether groupings (DE 3,544,165 and 3,601,264),

6. compounds having silyl enol ether groupings (DE 3,730,785 and3,730,783),

7. monoacetals or monoketals whose aldehyde or ketone component has asolubility in the developer between 0.1 and 100 g/l (DE 3,730,787),

8. ethers based on tertiary alcohols (U.S. Pat. No. 4,603,101) and

9. carboxylates and carbonates of tertiary, allylic or benzylic alcohols[U.S. Pat. No. 4,491,628 and J. M. Frechet et al., J. Imaging Sci. 30:59-64 (1986)].

These materials can also be present as mixtures. In this case it ispreferred that the acid-cleavable materials correspond to only one ofthe above-mentioned types, including here with particular preferencethose having at least one acid-cleavable C--O--C bond, i.e., thosebelonging to types (1), (2), (7) and (9). Under type (2), the polymericacetals and, from the acid-cleavable materials of type (7), especiallythose derived from aldehydes or ketones having a boiling point aboveabout 150° C. preferably above about 200° C., are to be singled out.

To the acid-cleavable compounds (b) contained in the radiation-sensitivemixture according to the invention, photolytic acid generators (a) areadded, for which purpose onium salts, such as diazonium, phosphonium,sulfonium and iodonium salts of non-nucleophilic acids, for example, ofHSbF₆, HAsF₆ or HPF₆ [J. V. Crivello, Polym. Eng. Sci., 23:953 (1983)]are suitable only with restrictions, since highly corrosive acids can begenerated. Photolytic acid generators that generate sulfonic acids onexposure are preferred. Examples of such compounds which may bementioned are 1,2-disulfones, bis-sulfonyl-diazomethane (DE 3,930,086)and sulfonyl-carbonyl-diazomethane (DE 3,930,087), nitrobenzylsulfonates (F. M. Houlihan et al., J. Photopolym. Sci. Techn., 3:259(1990); T. Yamaoka et al., J. Photopolym. Sci. Techn., 3:275 (1990)),pyrogallol sulfonates (L. Schlegel et al., J. Photopolym. Sci. Techn.,3:281 (1990)) or iminosulfonates (M. Shirai et al., J. Photopolym. Sci.Techn., 3:301 (1990)). Onium salts that generate perfluorosulfonic acidsand the 1-sulfonyloxy-2-pyridones mentioned in German Patent ApplicationP 4,112,967.9 are particularly preferred.

The photolytic acid generators are added to the mixture in a proportionof about 0.2 to 25% by weight. Proportions of about 0.5 to 15% by weightare preferred, and about 1 to 10% by weight, relative to the totalweight of the solid constituents of the mixture, are particularlypreferred, the nature of the components (a) to (c) determining themutual ratio of the compounds used.

The photolytic acid generators have absorption maxima in the rangebetween 200 and 500 nm. They fix the spectral sensitivity of themixtures according to the invention. They can be selected in such a waythat sensitivities as required in practice in the region of thetechnically important radiation sources, e.g., g-line (436 nm), i-line(365 nm) or UV-2 (248 nm), can be achieved. The acid-cleavable compounds(b) that can be used according to the invention can here be selectedsuch that they have virtually no characteristic absorption in theseregions. By means of spectral sensitization, the sensitivity range ofthe acid-generating compounds (a) can be widened to such an extent thatradiation sources of the visible region or shortwave X-ray region canalso be used. Finally, other radiation sources, such as electron beamsor ion beams, can also be used for the imagewise differentiation of themixture according to the invention, especially if highly active acidgenerators (EP 0,318,649) are employed.

The radiation-sensitive mixture according to the invention also containsat least one polymeric binder (c) that is insoluble in water but solubleor at least swellable in aqueous-alkaline solutions. The selection ofthe suitable binder depends largely on the type of use. The binder isespecially distinguished by the fact that it readily dissolves theconstituents of the radiation-sensitive mixture according to theinvention, permits aqueous-alkaline developability and especially hasthe lowest possible characteristic absorption, i.e., high transparency,especially in the wavelength range of the incident radiation from 190 to550 nm.

For the conventional applications, i.e., using light sources in thenear-UV region, binders based on novolak condensation resins, that havegenerally been used in combination with naphthoquinonediazides asphotoactive components, are particularly suitable for this purpose. Suchphenol/formaldehyde condensates have been described many times and cancontain, as the phenolic component, phenol, the three positionallyisomeric cresols or other alkylphenols, e.g., xylenols, as components.In addition to formaldehyde, other aldehydes can also be utilized forpreparing the polymer. The polymers containing hydroxyl groups, that aredescribed below, can equally well be used for irradiations with near-UVlight.

Other polymeric materials are, however, necessary for applications inthe UV-2 region. Novolaks that as a rule are used in combination withnaphthoquinonediazides as photoactive components are unsuitable for thispurpose. They can, however, be used as a mixture with other resinssuitable as binders and having a higher transparency. The mixing ratiosthen depend predominantly on the nature of the binder to be mixed withthe novolak resin. In particular, the degree of characteristicabsorption thereof in the specified wavelength region and also themiscibility with the other constituents of the radiation-sensitivemixture then play a decisive part. In general, however, the binder ofthe radiation-sensitive mixture according to the invention can containup to about 50% by weight and especially up to about 20% by weight of anovolak condensation resin.

Suitable binders are homopolymers or copolymers of p-hydroxystyrene andof its alkyl derivatives, for example, of 3-methyl-4-hydroxystyrene, of3,5-dimethyl-4-hydroxystyrene or of 2,3-dimethyl-4-hydroxystyrene, andhomopolymers or copolymers of other polyvinylphenols, for example, of3-hydroxystyrene, or of 4-methyl-3-hydroxystyrene or the esters of(meth)acrylic acid with phenols, for example, pyrocatechol, resorcinol,hydroquinone or pyrogallol, or aminophenols, and the correspondingamides with aromatic amines. The comonomers used can be polymerizablecompounds such as styrene, methyl methacrylate, methyl acrylate or thelike.

Mixtures of enhanced plasma resistance are obtained ifsilicon-containing vinyl monomers, for example, vinyl trimethylsilane orallyltrimethylsilane, are used for the preparation of copolymers of theabove type. The transparency of these binders in the region of interestis generally higher, so that improved imaging is possible.

Homopolymers or copolymers of maleimide can also be used equally well.These binders again show high transparency in the wavelength regiondescribed. Here again, the comonomers used are preferably styrene,substituted styrenes, vinylphenols, vinyl ethers, vinyl esters,vinylsilyl compounds or (meth)acrylates.

Finally, copolymers of styrene with comonomers that effect an increasein the solubility in aqueous-alkaline solutions can also be used. Theseinclude, for example, maleic anhydride and maleic acid half-esters.

The binders can be mixed with one another if the optical quality of theradiation-sensitive mixture is not adversely affected thereby. However,binder mixtures are not preferred.

The quantity of the binder is generally about 30 to 95% by weight,especially about 40 to 90% by weight and preferably about 50 to 85% byweight, relative to the total weight of the solid constituents of theradiation-sensitive mixture.

The extinction of the binder or of the combination of binders forradiation of the wavelength from about 220 to 500 nm should be less thanabout 0.5, preferably less than about 0.3 μm⁻¹.

If appropriate, dyes, pigments, plasticizers, wetting agents andleveling agents, and also polyglycols, cellulose ethers, e.g.,ethylcellulose, can also be added to the radiation-sensitive mixturesaccording to the invention in order to meet special requirements, suchas flexibility, adhesion and gloss.

If a substrate is to be coated, the radiation-sensitive mixtureaccording to the invention is appropriately dissolved in a solvent or ina combination of solvents. Particularly suitable for this purpose areethylene glycol and propylene glycol and the monoalkyl and dialkylethers derived therefrom, especially the monomethyl and dimethyl ethersand the monoethyl and diethyl ethers, esters derived from aliphatic (C₁-C₆)-carboxylic acids and either (C₁ -C₈)-alkanols or (C₁-C₈)-alkanediols or (C₁ -C₆)-alkoxy-(C₁ -C₈)-alkanols, for example,ethyl acetate, hydroxyethyl acetate, alkoxyethyl acetate, n-butylacetate, propylene glycol monoalkyl ether-acetate, especially propyleneglycol methyl ether-acetate, and amyl acetate, ethers such astetrahydrofuran and dioxane, ketones such as methyl ethyl ketone, methylisobutyl ketone, cyclopentanone and cyclohexanone,N,N-dialkyl-carboxamides such as N,N-dimethylformamide andN,N-dimethylacetamide, and also hexamethylphosphotriamide,1-methyl-pyrrolidin-2-one and butyrolactone, as well as any desiredmixtures thereof. Among these, the glycol ethers, aliphatic esters andketones are particularly preferred.

Ultimately, the selection of the solvent or solvent mixture depends onthe coating process used, on the desired layer thickness and on thedrying conditions. In addition, the solvents must be chemically neutral,i.e., they must not irreversibly react with the other layer components.

The solution prepared with the solvents generally has a solids contentof about 5 to 60% by weight, preferably up to about 50% by weight.

Finally, the invention also relates to a radiation-sensitive recordingmaterial comprising a substrate and a radiation-sensitive layer composedof the radiation-sensitive mixture according to the invention.

The substrates can be all those materials of which capacitors,semiconductors, multi-layer printed circuits or integrated circuits arecomposed or from which these can be prepared. Silicon substrates, thatoptionally have been thermally oxidized and/or coated with aluminum ordoped, deserve special mention. In addition, all other substratesconventional in semiconductor technology are possible, such as siliconnitride, gallium arsenide and indium phosphide. The substrates knownfrom liquid crystal display production can also be used, such as glassor indium/tin oxide, and also metal plates and foils, for example, ofaluminum, copper and zinc, bimetal foils and trimetal foils, and alsoelectrically non-conductive foils on which metals have beenvapor-deposited, and paper. These substrates can have been thermallypretreated, superficially roughened, incipiently etched or pretreatedwith chemicals to improve desired properties, for example, to enhancethe hydrophilic character.

In order to provide the radiation-sensitive layer with better cohesionand/or better adhesion to the substrate surface, it can contain anadhesion promoter. The same effect can be achieved by anadhesion-promoting interlayer. In the case of silicon substrates andsilica substrates, adhesion promoters of the aminosilane type, such as,for example, 3-aminopropyltriethoxysilane or hexamethyldisilazane, canbe used for this purpose.

Suitable supports for the production of photomechanical recordinglayers, such as printing forms for letterpress printing, planographicprinting, screen printing and flexographic printing, are especiallyaluminum plates that may be anodically oxidized, grained and/orsilicatized beforehand, and also zinc plates and steel plates which maybe chromium-plated, and also plastic films and paper.

The recording material according to the invention is exposed imagewiseto actinic radiation. Suitable radiation sources are especially metalhalide lamps, carbon arc lamps, xenon lamps and mercury vapor lamps.Exposure can also be carried out with high-energy radiation such aslaser radiation, electron beams or X-rays. However, lamps that can emitlight of a wavelength from 190 to 260 nm, i.e., especially xenon lampsand mercury vapor lamps, are particularly preferred. Furthermore, laserlight sources can also be used, e.g., excimer lasers, especially KrF orArF lasers, that emit at 248 or 193 nm, respectively. The radiationsources must show an adequate emission within the wavelength ranges.

Within the scope of this description, actinic radiation is to beunderstood as any radiation whose energy corresponds at least to that ofshortwave visible light. Longwave and shorter-wave UV radiation such asis emitted, for example, by excimer lasers, is therefore particularlysuitable.

The thickness of the light-sensitive layer depends on the intended use.It is generally between about 0.1 and about 100 μm, preferably between 1and 10 μm.

The invention further relates to a process for producing aradiation-sensitive recording material. The application of theradiation-sensitive mixture to the substrate can be effected byspraying, flow-coating, roller application, whirler-coating anddip-coating. Subsequently, the solvent is removed by evaporation, sothat the radiation-sensitive layer remains on the surface of thesubstrate. The removal of the solvent can be promoted by heating thelayer to temperatures of up to about 150° C. The mixture can, however,also be applied first in the above-mentioned way to a temporary support,from which it is transferred under pressure and at an elevatedtemperature to the final support material. The temporary supports usedcan in principle be any material that is suitable as support material.Subsequently, the layer is irradiated imagewise. It is then treated witha developer solution that dissolves and removes the irradiated areas ofthe layer, so that an image of the original used in the imagewiseirradiation remains on the substrate surface.

Suitable developers are especially aqueous solutions that containsilicates, metasilicates, hydroxides, hydrogen phosphates and dihydrogenphosphates, carbonates or hydrogen carbonates of alkali metal ions,alkaline earth metal ions and/or ammonium ions, and also ammonia and thelike. Metal ion-free developers are described in U.S. Pat. No.4,729,941, EP 0,062,733, U.S. Pat. No. 4,628,023, U.S. Pat. No.4,141,733, EP 0,097,282 and EP 0,023,758. The content of thesesubstances in the developer solution is generally about 0.1 to 15% byweight, preferably about 0.5 to 5% by weight, relative to the weight ofthe developer solution. Metal ion-free developers are preferably used.Small quantities of a wetting agent can have been added to thedevelopers in order to facilitate the detachment of the soluble areas ofthe layer.

The developed layer structures can be posthardened. This generally iseffected by heating on a hotplate up to a temperature below the flowtemperature and subsequent whole-area exposure to the UV light of axenon/mercury vapor lamp (range from 200 to 250 nm). The imagestructures are crosslinked by the posthardening, so that they generallyhave a flow resistance up to temperatures of more than 200° C. Theposthardening can also be effected without an increase in temperature,solely by irradiation with high-energy UV light in a high dosage.

The radiation-sensitive mixture according to the invention is used inthe manufacture of integrated circuits or of individual electricalcomponents by lithographic processes, since they have a high lightsensitivity, particularly when irradiated with light of a wavelengthbetween about 190 and 300 nm. Since the mixtures bleach very well onexposure, finer structures can be achieved than is possible with theknown mixtures. The developed resist layer here serves as a mask for thesubsequent process steps. Examples of such steps are the etching of thelayer support, the implantation of ions into the layer support or thedeposition of metals or other materials on the layer support.

The examples described below illustrate the invention, but they are notintended to effect any restriction. Percentage data are always percentby weight, and melting points are uncorrected unless otherwise stated.P.b.w. means parts by weight below.

EXAMPLE 1

1st stage: Preparation of 4-tert.-butoxycarbonyloxy-benzaldehydedimethylacetal

Two g (9 mmol) of 4-(tert.-butoxycarbonyloxy)-benzaldehyde weredissolved at room temperature in 10 ml of methanol and 1.2 ml oftrimethyl orthoformate. To obtain complete solution, 1.5 ml of toluenewere added. This was followed by the addition of 3.75 mg of RhCl₃ [CH₃C(CH₂ PPh₂)₃ ] as catalyst. The mixture was then stirred overnight atroom temperature. The solvents were separated off by steam distillationand the oily residue was taken up in a little toluene. The rhodiumcatalyst was filtered off over a G-4 frit. After the toluene had beenstripped off under reduced pressure, the product was dried in an oilpump vacuum.

Yield 2.3 g (95% of theory) , pale yellow oil, H-NMR (CDCl₃): acetalsignal at 5.38 ppm, BOC signal at 1.56 ppm, CO signal in the IR spectrumat 1760 cm⁻¹ (compound 1) .

2nd stage: Preparation of an oligomer from4-tert.-butoxycarbonyloxy-benzaldehyde dimethylacetal and diethyleneglycol

A mixture of 1 g (3.73 mmol) of 4-(tert.-butoxycarbonyloxy)-benzaldehydedimethylacetal, 0.40 g (3.73 mmol) of diethylene glycol and 18 mg ofpotassium hydrogen sulfate was heated to the boil in 40 ml of driedtoluene under a reflux condenser. After heating for 2 hours, themethanol formed was distilled off slowly, while more toluene was addedto the mixture. After complete removal of the methanol, the mixture wascooled down, the potassium hydrogen-sulfate catalyst was filtered offand the toluene was stripped off. The yellowish, viscous residue wasdried in an oil pump vacuum.

Yield 0.8 g (57% of theory); H-NMR (CDCl₃): acetal signal at 5.68 ppm,BOC signal at 1.55 ppm, CO signal in the IR spectrum at 1760 cm⁻¹(compound 2).

EXAMPLE 2 Preparation of an oligomer from4-tert.-butoxycarbonyloxy-benzaldehyde dimethylacetal and1,4-butanediol.

One g (3.73 mmol) of 4-tert.-butoxycarbonyloxy-benzaldehydedimethylacetal, prepared according to Example 1, 1st stage, wasdissolved in 40 ml of dried toluene. After addition of 0.34 g (3.73mmol) of 1,4-butanediol and 18 mg of potassium hydrogensulfate, theresulting mixture was stirred for 2 hours under reflux. The methanolformed was then distilled off slowly, while more toluene was added tothe mixture. After complete removal of the methanol, the mixture wascooled down and the potassium hydrogensulfate was filtered off. Thefiltrate was concentrated in a rotary evaporator. This gave a yellowish,viscous oil, which was dried in an oil pump vacuum.

Yield 0.75 g (56% of theory). H-NMR (CDCl₃): acetal signal at 5.39 ppm,BOC signal at 1.57 ppm, CO signal in the IR spectrum at 1760 cm⁻¹(compound 3).

EXAMPLE 3

1st stage: Preparation of3-methoxy-4-tert.-butoxycarbonyloxy-benzaldehyde diethylacetal

An amount of 1.52 g (6 mmol) of3-methoxy-4-tert.-butoxycarbonyloxy-benzaldehyde was dissolved in 18 mlof ethanol and 2 ml of triethyl orthoformate. For complete solution ofthe 3-methoxy-4-tert.-butoxycarbonyloxy-benzaldehyde, a further 2 ml oftoluene were added. This was followed by the addition of 4.2 mg of RhCl₃[CH₃ C(CH₂ PPh₂)₃ ] as catalyst. The reaction solution was then stirredat room temperature until starting material was no longer detectable inthe thin-layer chromatogram. After the solvents had been stripped off,the oily residue was dissolved in a little toluene and filtered over aG-4 frit. The resulting solution was concentrated in a rotary evaporatorand dried in an oil pump vacuum.

Yield 1.72 g (88% of theory), pale yellow oil, H-NMR (CDCl₃): acetalsignal at 5.44 ppm, BOC signal at 1.55 ppm, CH₃ O signal at 3.73 ppm, COsignal in the IR spectrum at 1760 cm⁻¹ (compound 4).

2nd stage: Preparation of an oligomer from3-methoxy-4-tert.-butoxycarbonyloxy-benzaldehyde diethylacetal and2-butyne-1,4-diol:

An amount of 1.1 g (3.36 mmol) of3-methoxy-4-tert.-butoxycarbonyloxy-benzaldehyde diethylacetal wasdissolved in 40 ml of dried toluene. After the addition of 0.31 g (3.36mmol) of 2-butyne-1,4-diol and 18 mg of potassium hydrogen sulfate, themixture was further processed as described in Example 2.

Yield 0.8 g (80% of theory), H-NMR (CDCl₃): acetal signal at 5.37 ppm,BOC signal at 1.55 ppm (compound 5).

EXAMPLE 4

1st stage: Preparation of 2,3-bis-tert.-butoxycarbonyloxy-benzaldehydedimethylacetal.

Three g (9 mmol) of 2,3-bis-tert.-butoxycarbonyloxy-benzaldehyde weredissolved at room temperature in 10 ml of methanol and 1.2 ml oftrimethyl orthoformate. For complete dissolution of the benzaldehydederivative, 1.5 ml of toluene were added. This was followed by theaddition of 3.75 mg of RhCl₃ [CH₃ C(CH₂ PPh₂)₃ ] as catalyst. Themixture was then stirred overnight at room temperature. The solventswere separated off by steam distillation and the oily residue was takenup in a little toluene. The undissolved rhodium catalyst was filteredoff over a G-4 frit. After the toluene had been stripped off underreduced pressure, the product was dried in an oil pump vacuum.

Yield 2.9 g (75% of theory), pale yellow oil, H-NMR (CDCl₃): acetalsignal at 5.30 ppm, BOC signal at 1.55 ppm, CO signal in the IR spectrumat 1760 cm⁻¹.

2nd stage: Preparation of an oligomer from2,3-bis-tert.-butoxycarbonyloxy-benzaldehyde dimethylacetal and1,4-bis(2-hydroxyethoxy)-benzene:

An amount of 1.92 g (5 mmol) of2,3-bis-tert.-butoxycarbonyloxy-benzaldehyde dimethylacetal wasdissolved in 50 ml of dried toluene. After the addition of 0.99 g (5mmol) of 1,4-bis(2-hydroxyethoxy)-benzene and 25 mg of potassiumhydrogen sulfate, the mixture was further processed as in Example 2.

Yield 2.2 g (86% of theory), H-NMR (CDCl₃): acetal signal at 5.31 ppm,BOC signal at 1.54 ppm (compound 7).

The structural formulae of compounds 1 to 7 are shown below. ##STR6##

EXAMPLES 5 to 20

The examples described below were prepared analogously to theinstructions given in Example 1, only slight changes in the reactiontime and working-up being made in individual cases. All the compoundswere unambiguously identifiable by elemental analysis, H-NMR and the IRspectrum. ##STR7##

APPLICATION EXAMPLE 1

A coating solution was prepared from:

7.5 p.b.w. of a cresol/formaldehyde novolak having a softening rangefrom 105° to 120° C.,

2.0 p.b.w. of compound 2,

0.4 p.b.w. of6-(4-chlorostyryl)-4-methyl-1-trifluoromethanesulfonyloxy-2-pyridone and

42 p.b.w. of propylene glycol monomethyl etheracetate.

The solution was filtered through a filter of 0.2 μm pore diameter andwhirler-coated at 3,200 rpm onto a wafer treated with an adhesionpromoter (hexamethyldisilazane). After drying at 100° C. for 1 minute onthe hotplate, a layer thickness of 1.1 μm was obtained.

The recording material was exposed imagewise under an original to theradiation of a xenon/mercury vapor lamp at 365 nm with an energy of 65mJ/cm². To complete the cleavage of the solution inhibitor, the materialwas heated for 1 minute to 100° C.

The recording material was developed with a purely aqueous developerthat contained 2.38% by weight of tetramethylammonium hydroxide.

After a developing time of 120 seconds, this gave a perfect image of themask with steep resist flanks, even structures of less than 0.55 μmbeing resolved in true detail. An examination of the flanks of theresist profiles by scanning electron microscopy showed that these werealigned virtually perpendicular to the substrate surface. The contrastwas 5.6.

The contrast of a positive resist, c_(p), is defined as

    c.sub.p 1/(log D.sub.p -log D.sub.p.sup.o)=[log(D.sub.p /D.sub.p.sup.o).sup.-1

where D_(p) ^(o) is the incident radiation dose at which the developerstarts to attack the exposed film, and D_(p) is the resist referencepoint (=resist sensitivity). A precise description of this parameter isgiven in the article by L. F. Thompson and M. J. Bowden "ResistProcessing" (Introduction to Microlithography, Theory, Materials andProcessing, editors C. G. Willson, L. F. Thompson and M. J. Bowden, ACSSymp. Ser., 219:164 et seq. (1983), American Chemical Society,Washington).

APPLICATION EXAMPLE 2

A coating solution was prepared from:

7.5 p.b.w. of a copolymer of3,5-dimethyl-4-hydroxystyrene/4-hydroxystyrene (molar ratio 30:70)having a mean molecular weight of 25,000,

2.0 p.b.w. of compound 2, and

0.4 p.b.w. of triphenylsulfonium trifluoromethane-sulfonate in

42 p.b.w. of propylene glycol monomethyl ether-acetate.

The solution was filtered through a filter of 0.2 μm pore diameter andwhirler-coated at 3,300 rpm onto a wafer treated with an adhesionpromoter (hexamethyldisilazane). After drying for 1 minute at 100° C. alayer thickness of 1.04 μm was obtained.

The recording material was exposed imagewise under an original to theradiation of a xenon/mercury vapor lamp at 240 to 260 nm with an energyof 31 mJ/cm², heated for 75 seconds to 100° C. and then processed usingthe developer described in Application Example 1.

After a developing time of 60 seconds, this gave a perfect image of themask with high flank stability, here again structures of less than 0.4μm being resolved in true detail.

APPLICATION EXAMPLE 3

A coating solution was prepared from:

7.5 p.b.w. of a copolymer of styrene and maleimide (molar ratio 1:1)having a softening range from 165° to 180° C.,

2.0 p.b.w. of compound 7, and

0.3 p.b.w. of triphenylsulfonium trifluoromethane-sulfonate in

42 p.b.w. of cyclohexanone.

The solution was filtered through a filter of 0.2 μm pore diameter andwhirler-coated at 3,200 rpm onto a wafer treated with an adhesionpromoter (hexamethyldisilazane). After drying for 1 minute at 100° C., alayer thickness of 1.12 μm was obtained.

The recording material was exposed imagewise under an original to theradiation of a xenon/mercury vapor lamp at 240 to 260 nm with an energyof 38 mJ/cm².

The recording material was developed using a 0.02N aqueoustetramethylammonium hydroxide solution, the exposed areas being detachedwithin 60 seconds without leaving a residue.

This again gave a perfect image of the mask with steep resist flanks.The removal of material in the dark was less than 20 nm; even structuresof less than 0.4 μm were resolved in true detail.

APPLICATION EXAMPLE 4

A coating solution was prepared from:

7.5 p.b.w. of a homopolymer of 3-methyl-4-hydroxystyrene having a meanmolecular weight of 25,000,

2.0 p.b.w. of compound 3, and

0.4 p.b.w. of 4-methyl-6-phenyl-1-trifluoromethanesulfonyloxy-2-pyridonein

42 p.b.w. of propylene glycol monomethyl etheracetate.

The solution was filtered through a filter of 0.2 μm pore diameter anddivided into two equal parts. One part was whirler-coated at 3,300 rpmonto a wafer treated with an adhesion promoter (hexamethyldisilazane).After drying for 1 minute at 100° C., a layer thickness of 1.08 μm wasobtained.

The recording material was exposed imagewise under an original to theradiation of a xenon/mercury vapor lamp at 240 to 260 nm with an energyof 75 mJ/cm², heated for 75 seconds to 100° C. and then processed usingthe developer described in Application Example 1.

After a developing time of 60 seconds, this gave a perfect image of themask with high flank stability, here again structures of less than 0.4μm being resolved in true detail.

The second part was subjected to the same procedure after storage in arefrigerator for 20 weeks. Identical results were obtained. This showsthat the mixture has extraordinarily good stability in solution.

APPLICATION EXAMPLE 5

The material described in Application Example 1 was exposed imagewise toradiation of a wavelength of 436 nm. After the processing described inApplication Example 1, a correct reproduction of the original down to0.55 μm was observed.

What is claimed is:
 1. A positive-working radiation-sensitive mixture,comprising:(a) a compound that generates a strong acid under the actionof actinic radiation, (b) a compound having at least one C--O--C bondthat can be cleaved by the acid generated by the compound (a), saidcompound represented by the formula I ##STR8## in which X is a phenyl,(1)paphthyl or (2)naphthyl radical that is substituted by at least onetert.-butoxycarbonyloxy group and optionally by further substituents, R¹is a hydrogen atom, a (C₁ -C₆)-alkyl radical, a (C₆ -C₁₀)-aryl radicalor one of the radicals X, R² is a (C₄ -C₁₂)-alkylene, (C₄-C₁₂)-alkenylene or (C₄ -C₁₂)-alkynylene group in which up to threemethylene groups are optionally replaced by bridge members having atleast one hetero atom, said bridge members being selected from the groupconsisting of --O--, --S--, --NR³ --, --CO--, --CO--O--, --CO--NH--,--O--CO--NH--, --NH--CO--NH--, --CO--NH--CO--, --SO₂ --, --SO₂ --O--,--SO₂ --NH--, a (C₄ -C₁₂)-cycloalkylene radical, a (C₄-C₁₂)-cycloalkenylene radical, and a (C₈ -C₁₆)-arylenebisalkyl radical,up to three methylene groups of the aliphatic moiety of the (C₈-C₁₆)-arylenebisalkyl radical being optionally replaced by bridgemembers of the above-mentioned type and the aromatic moiety of the (C₈-C₁₆)-arylenebisalkyl radical being optionally substituted by fluorine,chlorine or bromine atoms or by (C₁ -C₄)-alkyl, (C₁ -C₄)-alkoxy, nitro,cyano or tert.-butoxycarbonyloxy groups, R³ being an acyl radical, and nbeing an integer from 2 to 50, and (c) a binder that is insoluble inwater but soluble or at least swellable in aqueous-alkaline solution. 2.The positive-working radiation-sensitive mixture as claimed in claim 1,wherein R³ is a (C₁ -C₆)-alkanoyl radical.
 3. The positive-workingradiation-sensitive mixture as claimed in claim 1, wherein n is aninteger from 5 to
 20. 4. The positive-working radiation-sensitivemixture as claimed in claim 1, wherein X is substituted by a memberselected from the group consisting of a fluorine atom, a chlorine atom,a bromine atom, an iodine atom, a nitro group, a cyano group, a carboxylgroup, a (C₁ -C₉)-alkyl radical in which up to three methylene groupsare optionally replaced by a bridge member as recited in claim 1, aphenyl radical optionally substituted by a member selected from thegroup consisting of a tert.-butoxycarbonyl group, a (C₁ -C₄)alkylradical, a (C₁ -C₄)-alkoxy radical, a halogen atom, a (C₈ -C₁₂)-aralkylradical in which up to two methylene groups are optionally replaced by abridge member as recited in claim 1, a (C₆ -C₁₀)-aryloxy radical, and a(C₇ -C₁₀)-aralkoxy radical.
 5. The positive-working radiation-sensitivemixture as claimed in claim 1, wherein X is substituted by a memberselected from the group consisting of a fluorine atom, a chlorine atom,a bromine atom, an iodine atom, a nitro group, a cyano group, a carboxylgroup, a (C₁ -C₆)-alkyl radical in which up to three methylene groupsare optionally replaced by a bridge member as recited in claim 1, aphenyl radical optionally substituted by a member selected from thegroup consisting of a tert.-butoxycarbonyl group, a (C₁ -C₄)alkylradical, a (C₁ -C₄)-alkoxy radical, a halogen atom, a (C₈ -C₁₀)-aralkylradical in which up to two methylene groups are optionally replaced by abridge member as recited in claim 1, a (C₆ -C₁₀)-aryloxy radical, and a(C₇ -C₁₀)-aralkoxy radical.
 6. The positive-working radiation-sensitivemixture as claimed in claim 1, wherein R¹ is a hydrogen atom.
 7. Thepositive-working radiation-sensitive mixture as claimed in claim 1,wherein X is a substituted phenyl radical.
 8. The positive-workingradiation-sensitive mixture as claimed in claim 1, wherein compound (a)generates a sulfonic acid under the action of actinic radiation.
 9. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 0.25 to 25% by weight of compound (a), relative to thetotal weight of the solid constituents of the mixture.
 10. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 0.5 to 15% by weight of compound (a), relative to thetotal weight of the solid constituents of the mixture.
 11. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 1.0 to 10% by weight of compound (a), relative to thetotal weight of the solid constituents of the mixture.
 12. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 1 to 60% by weight of compound (b), relative to thetotal weight of the solid constituents of the mixture.
 13. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 5 to 50% by weight of compound (b), relative to thetotal weight of the solid constituents of the mixture.
 14. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 30 to 95% by weight of binder (c), relative to thetotal weight of the solid constituents of the mixture.
 15. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 40 to 90% by weight of binder (c), relative to thetotal weight of the solid constituents of the mixture.
 16. Thepositive-working radiation-sensitive mixture as claimed in claim 1,comprising about 50 to 85% by weight of binder (c), relative to thetotal weight of the solid constituents of the mixture.
 17. Aradiation-sensitive recording material, comprising:a substrate; and alayer comprising a mixture as claimed in claim 1 coated on saidsubstrate.